Could you please specify, every time you’re referring as “disabling the antivirus” (when for example EMC is crashing all of a sudden), could you please advise, what actual feature of antivirus you suggest to disable? Antivirus has lots of features. Are you suggesting to disable all of them completely?
As @Gary said, all of them. But, for a smaller issue, Avira seems to cause the most problems for the most programs. Best to uninstall that one.
For others, many antivirus program have a feature where they setup a Man in the Middle. Because email is transported encrypted, an antivirus cannot scan it for incoming viruses until it is on the drive decrypted. So, the antivirus sets up a fake server and intercepts your mail, and then resends it. When in comes in, they intercept it, decrypt it and check for viruses. This internal firewall is often done very very badly and often leads to problems.
I always turn this feature off any anti-virus and it is often the cause of various problems. I also don’t believe it is useful as their poorly designed man in the middle is more likely to create security flaws than find them.